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NATURE 



[July 26, 1894 



from Lyell, from Darwin, and from writers of text-books, 

 are evidences of the natural though exaggerated re- 

 action into scientific uniformitarianism, from the ancient 

 legendar)- prescientific cataclysmal period, when every- 

 thing was done in a hurry, and a week was an epoch of 

 serious moment in the earth's history. In the reactionary 

 period, on the contrary, it was customary to airily postu- 

 late a few thousand million centuries for any particular 

 achievement ; geologists then drew upon " a practically 

 unlimited bank of time, ready to discount any quantity 

 of hypothetical paper." Lord Kelvin by physical reason- 

 ing recalled them from this unnecessary vagueness, and 

 put into their hands new data, ascertained by observation 

 of the earth's crust of just as close and valid a character 

 as any inspection of strata or classification of fossil 

 remains, but of a kind more immediately amenable to 

 mathematical calculation ; he called for more data from 

 observers, and meanwhile treated in the light of present 

 knowledge the data already available, just as the observ- 

 ing geologists had endeavoured to treat ordinary strati- 

 graphical facts in the light of what they perceived to 

 be at the present time occurring near river-mouths and 

 coast-lines. 



And in thus discussing and drawing deductions from 

 terrestrial data, Sir Wm. Thomson was a true geologist. 

 If researches and discoveries concerning the past history 

 of the earth, in respect of age and temperature and 

 physical condition and length of day and exposure to 

 sunshine, are not geology, it is difficult to adduce 

 anything that has a right to that title. Yet Prof. 

 Huxley, in a peroration to an address to the 

 Geological Society of London in 1S69, on the sub- 

 ject of Sir Wm. Thomson's address to the Glasgow 

 Society the year before, speaks of " the cry for reform 

 which has been raised from without," says " the case 

 against us has entirely broken down," and concludes 

 with the comfortable assurance : " we have exercised a 

 wise discrimination in declining to meddle with our 

 foundations at the bidding of the first passer-by who 

 fancies our house is not so well built as it might be.'' 



And another more astounding but very characteristic 

 sentence occurs in an earlier part of this forensic 

 speech : — 



"I do not suppose that at the present day any geologist 

 would be found to maintain absolute uniformitarianism, 

 to deny that the rapidity of the rotation of the earth may 

 be diminishing, that the sun vtay be waxing dim, or that 

 the earth itself may be cooling. Most of us, 1 suspect, 

 are Gallios, ' who care for none of these things,' being of 

 opinion that, true or fictitious, they have made no 

 practical difference to the earth, during the period of 

 which a record is preserved in stratified deposits." 



This attitude of "not caring " for the results of scien- 

 tific investigation in unpopular regions, even if those 

 results be true, is very familiar to some of us who arc 

 engaged in a quest which both the great leaders in the 

 above-remembered controversy agree to dislike and de- 

 spise. It is an attitude appropriate to a company of share- 

 holders, it is a common and almost universal sentiment 

 of the noble army of self-styled " practical men," but it 

 15 an astonishing attitude for an acknowledged man of 

 science, whose whole vocation is the discovery and 

 leccption of new truth. 



NO. i2gi. VOL. 50] 



Certain obscure facts have been" knocking at the door 

 of human intelligence for many centuries, and they are 

 knocking now, in the most scientific era the world has yet 

 seen. It may be that they will have to fall back dis- 

 appointed for yet another few centuries, it may be that 

 they will succeed this time in efi'ecting a precarious and 

 constricted right of entry ; the issue appears to depend 

 upon the attitude of scientific men of the present and 

 near future, and no one outside can help them. 



I admit that it savours of presumption even to quote in 

 a critical spirit from the utterances of a man of Prof. 

 Huxley's eminence, a man who fought with surpassing 

 eloquence and vigour the battle of free and open inquiry 

 into the facts of the universe before most of us had cut 

 our wisdom teeth ; but having been guilty of such an act 

 of presumption, I propose to cap it with another : 1 shall 

 take permission to say how cordially we recognise the 

 immense service to truth and progress which has been 

 effected by those gladiators who, in despite of fierce hos- 

 tility, and in face of deadly odds, encountered and over- 

 came the forces of superstition and won for us who follow 

 so great a measure of freedom and friendly countenance 

 as we now enjoy. 



It requires an eflTort of imagination now, or a visit to 

 some stagnant country town, to realise the strength 

 of prejudice which the evolutionary spirit of science 

 . ad at one time to encounter. It would ill beseem 

 us who are enjoying the peaceful outcome of this 

 struggle to regard with other than the deepest honour 

 those veterans who bore the burden of the fray, even 

 though they sometimes display their fighting front to 

 a left wing of earnest investigators who come heavily 

 marching over the bog and swamps not far removed from 

 those into which the conquered hosts retreated. The 

 morass is difficult and treacherous — it may once more be 

 overwhelming — but if ever secure foothold is gained, and 

 the mud on our clothing has time to dry, the veterans will 

 recognise their own colours and not the colours of their 

 former foes. 



Returning to our immediate subject, I pick out from 

 the address on Geological Time the following interesting 

 points. The tides are a case of forced vibration in 

 which the natural period of free swing is longer than 

 that corresponding to the forced period ; consequently, 

 but for friction, the tidal humps are at right angles to the 

 line of tide-generating force. Were the free period shorter 

 than the forced, the tidal humps would be in the line of 

 force, again excepting friction ; and were the two periods 

 the same, the tidal humps, but for friction, would be in- 

 finite. The fact th.it the natural or free period is longer, 

 not shorter, than the lunar or solar day period, as well 

 as the bare fact of appreciable friction itself, aic proved 

 by a delay in the occurrence of spring-tide, which again 

 establishes the fact that the lunar tide is more accelerated 

 by friction than is the solar tide ; the solar being of 

 slightly shorter period than the lunar, and therefore 

 slightly more discordant with the natural swing. 



The effect of friction is to accelerate the tidal phase» 

 and by this acceleration its amount can, or could if the 

 data were good enough, be estimated. It is equivalent 

 to a friction brake applied to the equator, and tightened 

 till it recjuires a total tangential force equal to the 

 ordinary weight of four million tons to hold it still. 



